Brazing alloy



United States Patent Ofiice 3,329,954 Patented May 16, 1967 The invention described herein may be manufactured and used by or for the Govemment of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to alloys and, in particular, to an alloy especially adapted for silver soldering and silver brazing purposes.

As may be known, there are several types of metals used in piping aboard ship. The pipe fittings, such as couplings, T joints and L joints, generally are made of bronzes known as G-metal and M-metal. The pipe used with the fittings has been made of oxidized copper or copper nickel (30% nickel). Although some difficulty has been experienced with all kinds of metal joints, the greatest difiiculty is in obtaining satisfactorily bonded joints when copper pipe is used in conjunction with bronze fittings. For example, when copper pipe has been used, the percent bonded area of the joint rarely has been in excess of 50% and most joints show approximately 40% to as low as 25%.

Several brazing aloys classifications have been approved and are in wide use by the US. Navy. Although these classifications range from so-called Grades 1 to V, only two of these alloys have been used in any quantity. The two most widely used are Grades III and V and of these two 90% or more of the pipe brazing is done with Grade HI.

An excellent reason why the Grade 111 brazing alloy is used to such an extent is that operators prefer it because of its melting range. For example, Grade 111 begins to melt of 1185 F. and finishes at about 1500 F. Grade V, however, begins at 1160 F. and finishes at 1175 F. In brazing large pipe sizes, the difference in the expansion of the pipe and fitting causes the tolerance between the pipe and fitting to exceed about 0.012 inch maximum and consequently there is a tendency for filler metal to run off the joints. When the operators use Grade III, they claim it melts slowly and the still solid metal holds the liquid metal in place until it is drawn into the adjacent joint lands by capillary action. Another advantage is that the phosphorus in Grade III makes it somewhat self-fluxing. When Grade V is used operators claim it becomes completely liquid quite rapidly and runs out on the floor.

Nevertheless, the Grade III alloy has serious faults metallurgically, one being that it does not wet copper pipe sufficiently and thus results in joints of low integrity. Another difficulty is that the phosphor forms a very brittle eutectic mixture with nickel and iron and should not be used in the presence of these elements.

It is, therefore, an object of the present invention to provide an alloy with a broad melting range as well as a good afiinity for copper and which also avoids the brittleness present when phosphorus mixes with nickel and iron.

The present alloy contains silver, copper, zinc, nickel, cadmium, and lithium, the ranges of these ingredients being substantially as follows:

Percent Silver 36 Copper g Zinc -30 Nickel 5*8 Cadmium 7 Lithium 0.02

Variations allowed in the analysis were plus or minus 2% for all elements. Alloys so formed were found to have a melting range of from 1200 to 1425 F.

Specific alloys tested had the following composition:

As will be appreciated the analyses and the melting and flow points necessarily are approximate.

The following table illustrates the improved bond obtained by the use of these new alloys, the data being provided by the use of Alloy #1 which, as will be noted, is compared with the previously-mentioned, widely-used Grade III alloy.

TABLE 1 Percent bond of 1%. I.P.S. joints that had pipe with grooved and serrated ends Joint Percent Number: Joint Condition Bond 1 Standard Groove Fittings-Grade III 27 2 Standard Groove Fittings-Grade III 27 3 Standard Groove Fittings-Grade III 33 4 Standard Joint-New Alloy 61 5 Standard Joint-New Alloy 61 6 Standard Joint-New Alloy 60 7 Standard Joint-New Alloy Obviously the new alloy has a good afiinity for copper. Also, as may be noted, it provides a sufiiciently broad melting range, which, as a practical matter, satisfies the operators and permits the brazing operations to be conducted without concern about run-01f. Further, the alloy does not employ phosphorus which metallurgically would preclude its use with nickel and iron alloys. Those familiar with this art will recognize similarities between the present alloy and others which have been employed for brazing purposes. Nevertheless it is the fact that no other alloy presently known provides the same practical and metallurgical advantages, which when coupled with the bond integrity, represent a distinct improvement in the particular brazing operations contemplated.

It is believed that the combination of both lithium and nickel is a significant factor in providing the difference in usability.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A brazing alloy consisting of about 36% silver, about 20% copper, zinc from about 25% to about 30%, nickel from about 5% to about 8%, about 7% cadmium, 0.02% lithium.

2. A brazing alloy consisting of about 36.37% silver, about 20.22% copper, about 30.29% zinc, about 5.2% nickel, about 7.19% cadmium and about 0.02% lithium the balance of the alloy consisting of minor variations in the recited percentages.

3. A brazing alloy consisting of about 36.37% silver, about 20.22% copper, about 25% zinc, about 8% nickel, about 7.19% cadmium, and about 0.02% lithium the balance of the alloy consisting of minor variations in the recited percentages.

References Cited by the Examiner UNITED STATES PATENTS 2,015,345 9/1935 Leach 75l34 2,235,634 3/1941 Hensel et al. 75-173 2,914,435 11/1959 Wasserman et al. 148-24 2,970,248 1/1961 Sahagun 317236 DAVID L. RECK, Primary Examiner.

H. SAITO, Examiner. 

1. A BRAZING ALLOY CONSISTING OF ABOUT 36% SILVER, ABOUT 20% COPPER, ZINC FROM ABOUT 25% TO ABOUT 30%, NICKEL FROM ABOUT 5% TO ABOUT 8%, ABOUT 7% CADMIUM, 0.02% LITHIUM. 